Harold Wilson, Labour leader for 13 years and prime minister for almost eight, has stunned the political world by announcing his resignation.

Mr Wilson, who turned 60 five days ago, made his bombshell announcement to his Cabinet this morning.

I have not wavered in this decision and it is irrevocable

Harold Wilson

The news came after he had been to Buckingham Palace to inform the Queen, although it is understood he had already confided his plans to the Monarch last December.

Revealing he had taken the decision to resign two years ago, he said: "I have not wavered in this decision and it is irrevocable."

Mr Wilson, who has served in Parliament for 31 years, said he intended to remain on the backbench of the Commons in an advisory role but would not interfere with government decisions.

Following his time at the top he said "no one should ask for more". He added he was resigning to allow others into the job.

He insisted there were no hidden reasons for his resignation.

It is understood before Mr Wilson told the Cabinet, he informed Chancellor Denis Healey, Foreign Secretary James Callaghan, and his own deputy, House of Commons Leader Edward Short.

The Cabinet responded by immediately issuing a statement expressing their shock and "deep regret", but they also paid tribute to his leadership which they said he had carried out with "outstanding wisdom and dedication".

A new party leader will be elected once Labour MPs have voted, which is expected to come within the next week or two.

The changeover will not involve an early general election.

Political tributes have been flooding in from across the political spectrum for the man who at 31 became the youngest Cabinet minister since William Pitt the Younger.

Harold Wilson remained the party's longest-serving prime minister until 6 February 2005, when his record was broken by Tony Blair.

He led the country from 1964 to 1970, and then again from 1974 to 1976 and came in on a pledge for change reflecting the mood for modernisation in the country.

Lord Wilson, as he became in 1983, introduced many permissive policies including the 1967 Sexual Offences Act which decriminalised homosexual practices above the age of consent and the 1967 Abortion Act, which legalised abortion under certain conditions.

But his government is also remembered for the deteriorating relations with trade unions and the devaluation of the pound in 1967.